Adjustments of rollers in a roller grinding mill



Sept. 3, 1957 G. R. LINDEN 2,805,028

ADJUSTMENTS 0F ROLLERS IN A ROLLER GRINDING MILL Gosfa R. Linden INVENToR.

AT TORNE YS G. R. LINDEN Sept. 3, 1957 ADJUSTMENTS OF ROLLERS IN A ROLLER GRINDING MILL Filed Oct. l, 1954 3 Sheets-Sheet 2k ATTORNEYS Sept. 3, 1957 G. R. LINDEN 2,805,028

Y`DJ.S'I`\UH'I'S OF' ROLL-ERS IN A ROLLER GRINDING MILL Filedoct. 1, 1954 3 sheets-sheet 5 Fig. 7

Fig. e

Gosfa R. Lindenlm/ENTOR.

AT TRNE Ys United States. Patent M ADJUSTMENTS F ROLLERS IN A ROLLER GRINDING MILL Gosta R. Linden, Park Ridge, N. J., assignor to J. M.

Lehmann Company, Inc., Lyndhurst, N. J., a corporation of New York Application October 1, 1954, Serial No. 459,599 4 Claims. (Cl. 241-159) This invention relates to roller grinding mills in which the material to be processed by the mill lis passed under pressure between the rollers of a train of rollers. More particularly, it relates to such a mill having one or more trains each of three rollers in which the position of at least one roller of each train is iixed and the positions of the other rollers are adjustable with relation to that of the tixed roller to vary the pressure therebetween.

Specifically this invention is directed to means in a roller grinding mill for accomplishing the adjustment of the pressures between the rollers in a train of three rollers wherein the position of one roller is xed.

A principal object of the present invention is to provide means in a roller grinding mill of the type described to produce pressure between each of the rollers in each train of rollers thereof and to adjust said pressures in which means no reactive forces resulting from the application of said pressures can be transmitted to the frame or any portion of themill except to the rollers themselves and to the means for producing said pressures. This object may be alternatively stated by saying that there is provided by the present invention in a roller grinding mill of the type described a system comprising the rollers, means for adjusting the pressures therebetween, means for regulating said pressures and means for readily observing said pressures which are completely oating with respect to the frame and other parts of the roller grinding mill.

A further object of the present invention is to provide means in a roller grinding mill of the type described by which the pressures between the rollers may be easily, quickly and very accurately adjusted to the precise pressures desired.

A further object of the present invention is to provide such means whereby these adjustments may be made and checked instantly at any moment during an operation period by workmen who have had practically no previous experience in the operation of such mills.

A still further object of the present invention is to provide such means by which the adjustment of pressure between the center roller of a train and the other rollers of said train may when so desired be made simultanei ously and in such a manner that said pressures at whatever adjustment chosen will always be of equal value.

It is a general object of the present invention to improve the construction of a roller grinding mill of the type described to be of economical construction and of simple, eicient and safe operation.

In my earlier Patent No. 2,592,048, issued April 8, 1952, there is disclosed and claimed hydraulic means in a roller grinding mill for adjusting the relative pressure between the rollers in a train of rollers in which the position of the center roller is fixed which have proved very successful in commercial practice. The adjusting means of that patent, however, although a distinct improvement over the prior art, are not completely oating from the frame and other parts of the mill. The result Y 2,805,028 Patented Se'pt. 3, 1 95'1 is that some reactive forces from the pressures applied between the rollers are transmitted to the frame and other parts of the mill which requires that the frame and other parts be of particularly sturdy construction. Furthermore, the'means of that patent do not permit the adjustment by one set of manual controls of the position and pressure between all the rollers of a train and therefore do not automatically insure that when desired the pressure between all rollers of the train will be equal.

While the present invention may be used in a roller grinding mill having the axes of its rollers in a vertical or any other plane as well as in a horizontal plane or in a roller grinding mill having three or more roller grinding mill having more than one train, it will be sufcient for invention to refer to its embodiments in a one train roller grinding mill having the axes of its rollers in a horizontal plane.

Other and further objects and advantages of the present invention will be obvious to those skilled in the art from the description of embodiments thereof as hereinbelow set forth more fully in the specification, drawings and claims.

In the drawings wherein like reference characters refer to like or corresponding parts throughout the several views:

Figure 1 is top view of a roller grinding mill embodying the invention,

Figure 2 is an end view thereof,

Figure 3 is a cross section on line 3-3 of Figure 1,

Figure 4 is a partial cross section on line 4 4 of Figure 1,

Figure 5 is a partial .cross section on line 5 5 of Figure 3,

Figure 6 is a partial cross section on line 6--6 of Fig-v ure 1, and l Figure 7 is a view similar to a part of the view of Fig-V ure 4 showing a modified use of the invention.

The roller grinding mill comprises a frame 10 in which is supported in a manner to be described more in detail hereinbelow a train of rollers comprising rollers 11, 12 and 13. The material to be processed by the roller grinding mill is introduced between rollers any suitable kind of hopper feeding device (not shown);` The material which has been processed is scraped off roller 13 by a scraper blade (not shown) and deposited thereby on discharge chute 14. In roller grinding mills having more than one train of rollers the material scraped off the last roller 13 may be introduced between two rollers of the second train in any suitable manner or the rst roller of the second train may be positioned adjacent last roller 13 of the rst train, so that the material being processed passes or ows directly between the last roller 13 of the first train and the irst roller of the next train.

VAny one or more of the rollers 11, 12 or 13 of the train is driven by an electric motor 15 or other power device through suitable transmission means. As shown in Figure 2 roller 13 is driven by motor 15 suitably mounted on frame 10V through drive chain 16 and the other rollers are driven therefrom by connecting them to that roller by gears 17 (see Figure 5), sprocket chains or in any other suitable manner. Since the method of driving the rollers forms no part of the present invention the details of the driving means are not shown. A structure generally designated as 18 and shown most clearly in Figures 3 and 4 serves to support the roller bearing assembly and the roller pressure adjustment means all to be more fully described hereinbelow and is anchored to frame 10 in any suitable manner as by bolts 19, 19 passing through ange sections 20, 20 of structure 18. Structure 18 may be described as being generally tri- 11 and 12 through' angular in shape with portions 21 and 22 extending horiz'dntally from eacliend of its base and portion 23 extending above its apex. Bearing 24 is formed in 18 near its apex to receive journal 25 of center roller 12 the portion-of structure 18 around bearing 25 is enlarged to form bearing housing 26. Pivot bearings 27 and ZS'are formed in extensions 21 and 22 respectively near their outer ends. Extension 23 is provided with an opening 29 providing a bearing surface for tension bar adjuster 39 toy be more fully described hereinbelow. Tension oar adjuster 3l) is provided with a keyway slot 31 (see Figure 4) and set screw 32 isrprovidred in extension 23 and adapted to extendinto keyway slot 31 to prevent rotation of tension bar adjuster in opening 29.

For one use of the present invention as shown particularly in Figures 3 and 4 removable means are provided for preventing sliding motion of tensionbar adjuster Sti in opening 29 thereby keeping the center of tension bar adjuster 30 at the center of opening 29. These means consist of holes 33 drilled transversely in extension 23 and locking pin 34 insertable therein and adapted to pass through a hole 35 (see Figure 7) bored through tension adjuster bar 3d in registry with holes 33. Pin 34 and nholes 33 and 3S into which it is readily insertable and from which it is readily removable should be accurately'machined so that there is n'o play therebetween. Swing bearing housings 37 and 3S have, as is clearly shown in Figures 3, 4 and 5, bearings 39 and 40 respectively in their forked lower extremities. Bearings 39 and 40 are adapted to receive bearing pivot pins 41 and 42 respectively which in turn are journaled in bearings 27 and 28. Bearings 39 and 40 are free to rotate on pivot pins 41 and 42 respectively which in turn are free to rotate in pivot bearings 27 and 28 respectively. Swing bearing housings 37 and 38 are provided near their other extremities with bearings 43 and 44 respectively each adapted to receive journals 45 and 46 of rollers 11 and 13 respectively. Each swing bearing housing 37 and 38 has an extension 47 and 48 each extending upwardly from the portion of housings 37 and 38 surrounding bearings 43 and 44 respectively. Holes 49 and 50 are provided in extensions 47 and 48 to receive tension bar adjuster 30 and are of suflicient size not only to permit tension bar adjuster 30 to slide therethrough but also to provide a small amount of radial clearance. Tension bar adjuster 30 as above described is provided with means comprising keyway 31 and set screw 32 for preventing its rotation in opening 29 and removable means comprising holes 33 and 35 and locking pin 34 for preventing its longitudinal motion in bearing 23 when such motion is not desired. Each end of tension bar'adjuster 30 is screw threaded as shown in detail at 51 in Figure 4 Vand is adapted to receive thereon internally screw threaded 52 adjustment shaft 53 thus forming a screw jack at each end. Adjustment sleeve54 surrounds adjustment shaft 53. It extends beyond the internally screw threaded end ofv adjustment shaft 53 at one end. Its other end passes through bearing 55 secured to frame 10 by any suitable means. Adjustment shaft 53, also extends outside of frame 10 where by means of pin 56 it, adjustment sleeve 54 and hand wheel 57 are secured together so that they all rotate as one unit and advance or retreat toward the center of the mill as one unit. Reference to Figure 3 will show a similar arrangement at the left side of the mill, as viewed in that figure, wherein 58 designates the adjustment sleeve, 60 the bearing in frame 10, 62 the pin and 64 the hand wheel. y y Compression springs 65 and 66 are positioned to encircle portions of tension bar adjuster 30, spring 65 abutting and extending between faces on extensions 23 and 47 and spring 66 abutting and extending between faces on extensions 23 and 48.

Hydraulic blocks 67 and 68 are slideably mounted on tension bar adjuster 30 so that they will be advanced toward the center of the mill by the advancing movement 4. of adjustment sleeves 54 and A58 respectively and so that plungers 69 and 70 abut against extensions 47 and 48 respectively and move them in the same direction when hydraulic blocks 67 and 68 are moved.

In each hydraulic block 67 and 68 a hydraulic cylinder 71 is formed into which plungers 69 and 70 are fitted as is shown in Figure 4 thus forming a hydraulic ram. Each hydraulic cylinder 71 is properly packed against pressure loss by any suitable type of packing such as that shown at 72, Figure 4, and is connected to a fixed volume hydraulic pressure registering system by iiexible connectors 73 and 74. The details of this system which are no part of the present invention are clearly shown in Figure 6. Flexible connector 73 leads through manifold 75 to sight reading pressure gauge 76 which is mounted'on frame 10 by retaining ring 77 or in anypother suitable manner. The hydraulic system is filled with an hydraulic fluid and any pressure exerted on plunger 69 will be registered on gauge 76. There is a complete and entirely separate hydraulic registering system and gauge as above described for each bearing housing of adjustable rollers 11 and 13 as is shown in Figure 3 wherein the pressure gauge is designated 78 andv in Figure 1 rwhen the pressure gauges for the bearing housings at the other end of the rollers are designated 76 and 78 respectively. The four pressure gauges 76 and 78 may be located in any convenient place but should be located so that they may be easily viewed by operator using the corresponding hand Wheel 57 or i The bearing support assembly and tension bar adjuster assembly described hereinabove serves to support and adjust the shaft or journals 25, 45 and 46 of one end of rollers 11, 12 and 13 respectively. These same assemblies are duplicated on the other side of the roller grinding mill to support the corresponding shafts or journals 25, 45 and 46 at the other end of rollers 11, 12 and 13 as is shown in Figure 1. i

Inserted through holes provided for that purpose on front and back walls of frame 10 are separation stou rods 79 and 80 held in position by check nuts 81 and 82 and adjustable by set screws 83 and 84. The purpose of separation stop rods 79 and 8,0 which are supplied for both ends of the rollers are to prevent the adjustable rollers from backing far enough to disengage driving gears 17 from their associate gears. The function of compression springs 65 and 66 is merely to keep rollers separated when the pressure exerted by turning hand wheels 57 and 64, as will be more fully explained hereinbelow, is decreased bel'ow a predetermined amount. Springs 65 and 66 therefore may be said to act as spacers for the rollers.

Connections to apply a heating or cooling medium to the rollers are shown at 85, 86, 87, 88 and 89. These connections form no part of the present invention and may be of any conventional type and arrangement. The embodiment of the invention shown in Figures 3 and 4 and described in connection therewith may be used under all conditions of operation but is of particular advantage whenA it is desired to have a different pressure between rollers 1 1 and 12 than that between rollers 12 and 13.' This requires operation of the two hand wheels 64 as well as thetwo hand wheels 57 as will be more fully explained hereinafter. When it is desired to have the same pressure between rollers 11 and 12 and between rollers 12`and 13V the arrangement shown in Figure 7 is of advantage. This differs from the arrangement shown in Figures 3 and 4 solely in the fact that locking pin 34 is removed from holes 33 and 35 so that tension bar adjuster 30 is free to slide in opening 29. This arrangement automatically insures that the pressure between rollers 11 and 12 and between rollers 12 and 13 will at all times be equal.

The operation Vof the device will now be briey described. v

Taking first the case where it is desired to have different pressures between rollers lliand 12 and between rollers 12 and 13, locking pin 34 will be inserted in holes 33 and 35 anchoring tension bar adjuster 30 at its center against any motion. To adjust the pressure between rollers 11 and 12 the operator turns one hand wheel 57 in the proper direction to increase or decrease the pressure as may be desired. Assuming the desired adjustment is an increase of pressure he turns hand wheel 57 in a direction to screw internally threaded portion 52 of adjustment shaft 53 on threaded portion 51 of tension bar adjuster 30. As viewed in Figures 3 and 4 this would be a clockwise direction as the operator views the mill from a position standing in front of it, that is, to the right as viewed in these figures. As hand wheel 57 is turned in this manner adjustment sleeve 54 and with it hydraulic block 67 is advanced toward the center of the mill thus exerting a force through plunger 69 on swing bearing housing extension 47 and causing it, swing bearing housing 37 and journal 45 of roller 11 to approach fixed bearing housing and support 18 and roller l2 and thus increase the pressure between rollers 11 and 12. It is obvious that this pressure will be transmitted by plunger 69 and hydraulic cylinder 71 to the hydraulic System connected to this adjustment control and to gauge 76 where it may be read by the operator. At the same time if feasible or immediately thereafter, the operator turns hand wheel 57 for the adjustment of journal 45 at the other end of roller 11 until the reading of pressure in gauge 76 for that adjustment system reaches the same value as that of gauge 76 of the first adjustment system.

The adjustment of the pressure between rollers 12 and 13 is laccomplished in exactly the same manner by turning hand wheels 64 in the proper direction and reading the pressure shown on gauges 78 which may or may not be the same as that shown on gauges 76 as may be desired. However, as is described hereinbelow when it is desired to have equal pressures between rollers 11 and 12 and between rollers 12 and 13, operation is simpler and more automatic if locking pin 34 is removed from holes 33 and 35.

With locking pin 34 removed from holes 33 and 35 as shown in Figure 7 it is obvious that tension bar adjuster 30 is free to slide in opening 29. Under this condition when hand wheel 57 is turned to screw up internally threaded portion 52 of adjustment shaft 53 on threaded portion 51 of tension bar adjuster 39 tension bar adjuster 30 moves a suilicient amount to the right as viewed in Figure 7 (also as viewed in Figures 3 and 4) to keep the midpoint of that portion of tension bar adjuster y30 between the inside ends of adjustment sleeves 54 and 58 at the center of opening 29. The result Vis that plunger 70, swing bearing housing 3S vand journal 46 of roller 13 will approach xed bearing housing and support 18 to the same extent that plunger 69, swing bearing housing 37 and journal 45 of roller 11 approaches it. To complete the adjustment the operator has only to turn hand wheel 57 for the journals at the other end of the roller to the proper position. The result is that the pressure between rollers 11 and 12 and between rollers 12 and 13 which may be read in gauge 76 or 78 is equal. No adjustment of hand wheels 64 is necessaryunder these conditions but, if so desired, vthe complete adjustment may be made by hand wheels 64 -instead of by hand wheels 57.

The description of the operation of the pressure adjustment devices has been described for the condition when it is desired to increase pressure. It is obvious that `-in all cases vdescribed above when it is desired to decrease pressure hand wheels 57 and or hand wheels 64, are turned in a direction so that internally threaded portions 52 of adjustment shafts 53 back off on threaded ends V51 of tension bar adjuster 3i?.

It should be noted that the forces exerted by springs 65 and 66 against extensions -47 -and 48 respectively are much less than the forces exerted against those elements bylplungers 69 and v70re`spectivelyY and are negligiblein all cases of normal operation.

From the above description of the arrangement of the parts and mode of operationthereof it is obvious that I have devised means for adjusting the pressure between the rollers of a three roller train in which the entire system may be said to be floating, that is, to keep all the direct forces and reactive forces entirely Within the adjustment system and to permit none of them to be transmitted to the frame or other parts of the mill. Thus, having reference to the apparatus when locking pin l34 is inserted in holes V33 and 35 it is-clear that the only places of mechanicalcontact of the adjustment assembly andv roller bearing housing and -support assembly with-other parts of the mill are at bearings-55 and 60 foradjustment sleeves 54 and 58 respectively and flange 20 on bearing support structure 18. Since adjustment sleeves 54 and 58 are tree to slide through bearings 55 and 60 respectively and since there are no forces present'here other than forces in an axial direction it is obviousno force can be transmitted to the frame at those places. The only forces exerted on-llange 20ofbearing support structure 18 other than the weight of the structure are negligible because they arise solely from external forces such as vibration. Indeed bolts -19 holding bearing support 18 in place are required only because of possible vibration or to hold bearing support structure l18 in place against any forces that might exist entirely external to the assemblies here under consideration. The connection of swing bearing housing 37 to base extension 21 is fully pivoted and therefore can transmit no torsional force to that member. The force originated by hand wheel 57 is transferred to plunger 69 and is balanced and neutralized by reactions at bearings 43 and 39 in swing bearing housing 37. The horizontal force at pivot pin bearing 27 is balanced and neutralized by reactions at bearing 24 and locking pin 34. The forces of swing bearing housing 38 are balanced and neutralized in a similar manner. Therefore, the sum of all the forces in this adjustment is zero within the parts mentioned and can be expressed in still another manner: forces at plunger 69 and locking pin 34 are equal and opposite, forces at bearings l43 and 24 are equal and op- Vposite and forces at bearings 39 and pivot pin bearing 27 are equal and opposite.

In the case where locking pin 34 is removed from holes 33 and 35 since tension bar adjuster 30 is free to slide in opening 29 it is obvious that no forces are transmitted at that place. Further, as is clear from the above description, when this pin is removed, the forces exerted by rollers 11 and 13 on fixed roller 12 and its bearing 24 are exactly balanced.

It is also obvious that I have devised means for adjusting the pressure between the rollers of a three roller train whereby when desired equal pressure is automatically obtained and maintained between all the rollers.

The arrangement of parts and method of their operation that I have disclosed permits a much more economical construction of a roller mill because the forces produced by exerting pressure between the rollers are contained entirely within the assemblies producing and regulating these ,pressures and are not transmitted to other parts of the mill. It is, therefore, possible to make the frame and other parts of the mill of much lighter construction than has heretofore been necessary.

What I claim is:

1. In a roller mill having a frame and at least one train of three rollers of which the position of the center roller is xed andthe position of each of the outside rollers of saidtrain is adjustable with respect to said center roller for each train ofrollers, a pair of bearings for said center roller each mounted in a bearing housing fixed to said mill frame, a pair of bearings for each of said ou'tside rollers each mounted in a bearing housing pivotally supported-on the vbearing housings 'for said center roller, portions of said bearing housings extending upwardly kfrom thel bearings respectively mounted therein, a pair of roller adjustment bars, openings in said upper portions of said bearing housings adapted to accommodate said roller adjustment bars and to permit them to slide through said openings, means in the openings in the pair of bearing housings for said center roller to prevent the rotation of said roller adjustment bars therewithin, bearing faces on the inside of the upper portions of said pivotally supported bearing housings and bearing faces on both sides of said bearing housings for the center roller, compres- 'vsion springs surroundingportions of each of said roller `adjustment bars and bearing respectively against said bearing faces, screw threaded ends on each end of each of said roller adjustment bars, internally screw threaded lic ram, connections from each of said cylinders to a pressure gauge, thus forming a constant volume hydraulic system, said hydraulic plungers disposed to abut against a portion of each of said pivotally supported bearing housings at a position below said respective roller adjustment bar and above the bearing in each of said housings to :exert a force on each of said bearing housings thus tending to move said housings simultaneously and in the same 'A amount toward the housings for said center roller.

2. In a roller mill having a frame and at least one train of three rollers of which the position of the center roller Vis fixed and the position of each of the outside rollers of said train is adjustable with respect to said center roller for each train of rollers, a pair of bearings for said center roller each mounted in a bearing housing fixed to said mill frame, a pair of bearings for each of said outside rollers each mounted in a bearing housing pivotally supported on the bearing housings for said center roller, portions of all said bearing housings extending upwardly from the bearings respectively mounted therein, a pair of roller adjustment bars, openings in said upper portions of said pivotally supported bearing housings adapted to accommodate said roller adjustment bars and to permit them to slide through said openings, means in said upper portions of said bearing housings for Said center roller adapted to accommodate said roller adjustment bars and to anchor said bars at their centers to said bearing housings and means in said last mentioned bearing housings to prevent the rotation of said roller adjustment bars therewithin, bearing faces on the inside of the upper portions of vsa-id pivotally supported bearing housings and bearing faces on both sides of said bearing housings for the center roller, compression springs surrounding portions of each of said roller adjustment bars and bearing respectively against said bearing faces, screw threaded ends on each end of each of said roller adjustment bars, internally screw threaded elements disposed to engage said screw threaded ends .and form screw jacks therewith, adjustment sleeves surrounding said elements, independent I' manually operable means for rotating each of said adjustment sleeves and each of said elements, blocks adapted to abut against the end of each of said adjustment sleeves and slideably mounted on said adjustment bars, hydraulic cylinders and plungers associated therewith in each of said blocks forming a hydraulic ram, connectionsfrom each of said cylinders to a pressure gauge thus'forming a constant volume hydraulic system, said hydraulic plungers disposed to abut against a portion of each of said pivotally supported bearing housings at a position below said respective roller adjustment bar and above the vbearing in each of said housings toexert forces independyentlfy on each of said bearing housings thus tending to molve saidr housings toward the housings for said center rol er.

3. In a roller mill having a frame and at least one train of three rollers of which the position of the center roller is fixed and the position of each of the outside rollers of said train is adjustable with respect to said center roller for each train of rollers, a pair of bearings for said center roller each mounted in a bearing housing xed'to said mill frame, a pair of bearings for each of said outside rollers each mounted in a bearing housing pivotally'supported on the bearing housings for said center roller, portions of all said bearing housings extending upwardly from the bearings respectively mounted therein, a pair of roller adjustment bars, openings in said upper portions of said bearing housings adapted to accommodate said roller adjustment bars `and to permit them to slide through said openings, means in the openings in the pair of bearing housings for said center roller to prevent the rotation of said roller adjustment bars therewithin, bearing faces on the inside of the upper portions of said pivotally supported bearing housings and bearing faces on both sides of said bearing housings for the center roller, compression springs surrounding portions of each of said roller adjustment bars land bearing respectively against said bearing faces, screw threaded ends on each end of each of said roller .adjustment bars, internally screw threaded elements disposed to engage said screw threaded ends and form screw jacks therewith, adjustment sleeves surrounding said elements, common manually operable means for rotating said adjustment sleeves and said elements, blocks adapted to abut against the end of each of said adjustment sleeves and slideably mounted on said adjustment bars, hydraulic cylinders and plungers associated therewith in each of said blocks forming a hydraulic ram, connections from each of said cylinders to a pressure gauge thus forming a constant volume hydraulic systemsaid hydraulic pluugers disposed to abut against a portion of each of said pivotally supported bearing housings to exert a force on each of said bearing housings thus tending to move said housings simultaneously and in the same amount toward the housings for said center roller. Y

4. In a roller mill having a frame and at least one train of three rollers of which the position of the center roller is iixed and the position of each of the outside rollers of said train is adjustable with respect to said center roller for each train of rollers, a pair of bearings for said center roller each mounted in a bearing housing xed to said mill frame, a pair of bearings for each of said outside rollers each mounted in a bearing housing pivotally supported on .the bearing housings for said center roller, portions of all said bearing housings extending upwardly from the bearings respectively mounted therein, a pair of roller adjustment bars, openings `in said upper portions of .said pivotally supported bearing housings adapted to accommodate said roller adjustment bars and to permit them to slide through said openings, means in vsaid upper portions of said bearing housings for said center roller adapted to vaccommodate said roller adjustment bars and to anchor said bars at their centers to said bearing housings and means in said last mentioned bearing housings to prevent .the'rotation of said roller adjustmentrbars therewithin, bearing faces on the inside of the'upper portions of said pivotally supported bearing housings and bearing faces on both sides of said bearing housings for the center roller, compression springs surrounding portions of each of said roller adjustment bars and bearing respectively against said bearing faces, screw threaded ends on each end of each of said roller adjustment bars, internally screw threaded elements disposed to engage said screw threaded ends and form screw jacks therewith, `adjustment sleeves surrounding said elements, independent manually operable means for rotating each of said adjust- Y ment sleeves and each of said elements, blocks adapted to abut against the end of each of Vsaid adjustment sleeves and slideably mounted on said adjustment bars, hydraulic cylinders and plungers associated therewith in each of said blocks forming a hydraulic ram, connections from ea-ch of said cylinders to a pressure gauge thus forming a constant volume hydraulic system, said hydraulic plungers disposed to abut against a portion of each of said pivot- -ally supported bearing housings to exert forces independently on each of said bearing housings thus tending to move said housings toward the housings for said center roller.

References Cited in the le of this patent UNITED STATES PATENTS Gilfert Sept. 7, 1886 Mawhood Feb. 19, 1889 Hawkins Apr. 30, 1940 Winslow Dec. 10, 1940 Linden Apr. 8, 1952 Hill July 28, 1953 FOREIGN PATENTS Germany Nov. 17, 1952 

